docs: def get_filetype_from_buffer(buf, max_lines=5):
      """
      Scan the buffer for modelines and return filetype if one is found.
      """
      lines = buf.splitlines()
      for l in lines[-1:-max_lines-1:-1]:
          ret = get_filetype_from_line(l)
          if ret:
              return ret
      for i in range(max_lines, -1, -1):
          if i < len(lines):
              ret = get_filetype_from_line(lines[i])
              if ret:
                  return ret
  
      return None